title: Linear- and angular-shaped naphthodithiophenes: selective synthesis, properties, and application to organic field-effect transistors.
abstract: A straightforward synthetic approach that exploits linear- and angular-shaped naphthodithiophenes (NDTs) being potential as new core structures for organic semiconductors is described. The newly established synthetic procedure involves two important steps; one is the chemoselective Sonogashira coupling reaction on the trifluoromethanesulfonyloxy site over the bromine site enabling selective formation of o-bromoethynylbenzene substructures on the naphthalene core, and the other is a facile ring closing reaction of fused-thiophene rings from the o-bromoethynylbenzene substructures. As a result, three isomeric NDTs, naphtho[2,3-b:6,7-b']dithiophene, naphtho[2,3-b:7,6-b']dithiophenes, and naphtho[2,1-b:6,5-b']dithiophene, are selectively synthesized. Electrochemical and optical measurements of the parent NDTs indicated that the shape of the molecules plays an important role in determining the electronic structure of the compounds; the linear-shaped NDTs formally isoelectronic with naphthacene have lower oxidation potentials and more red-shifted absorption bands than those of the angular-shaped NDTs isoelectronic with chrysene. On the contrary, the performance of the thin-film-based field-effect transistors (FETs) using the dioctyl or diphenyl derivatives were much influenced by the symmetry of the molecules; centrosymmetric derivatives tend to give higher mobility (up to 1.5 cm(2) V(-1) s(-1)) than axisymmetric ones (∼0.06 cm(2) V(-1) s(-1)), implying that the intermolecular orbital overlap in the solid state is influenced by the symmetry of the molecules. These results indicate that the present NDT cores, in particular the linear-shaped, centrosymmetric naphtho[2,3-b:6,7-b']dithiophene, are promising building blocks for the development of organic semiconducting materials.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan.
authors.forename: Shoji
authors.initials: S
authors.lastname: Shinamura
authors.forename: Itaru
authors.initials: I
authors.lastname: Osaka
authors.forename: Eigo
authors.initials: E
authors.lastname: Miyazaki
authors.forename: Akiko
authors.initials: A
authors.lastname: Nakao
authors.forename: Masakazu
authors.initials: M
authors.lastname: Yamagishi
authors.forename: Jun
authors.initials: J
authors.lastname: Takeya
authors.forename: Kazuo
authors.initials: K
authors.lastname: Takimiya
mesh_terms: D002627:Chemistry, Physical; D018360:Crystallography, X-Ray; D008567:Membranes, Artificial; D008958:Models, Molecular; D015394:Molecular Structure; D011789:Quantum Theory; D012666:Semiconductors; D013237:Stereoisomerism; D013876:Thiophenes / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D008567:Membranes, Artificial; D013876:Thiophenes